Battery management systems with adjustable charging current

• US 8,222,870 B2
• Filed: 03/31/2008
• Issued: 07/17/2012
• Est. Priority Date: 03/07/2007
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Guo, Jiankui, Tang, Ruichao, Li, Guoxing, Hou, Xiaohua, Zhang, Zhenming
• Primary Examiner(s): Fantu, Yalkew
• Application Number:
  US12/080,034
• Publication Number:
  US 20080218130A1
• Time in Patent Office: 1,569 Days
• Field of Search: 320/162, 320/134
• US Class Current: 320/162
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery management system includes a monitoring circuit and a charger. The monitoring circuit is operable for monitoring a battery pack that includes a plurality of cells, and for checking an unbalanced condition of the battery pack in each cycle of a plurality of cycles. The charger is operable for controlling a charging current to the battery pack and for receiving monitoring information from the monitoring circuit, and for adjusting the charging current from a first level in a previous cycle to a second level that is lower than the first level in response to a detection of the unbalanced condition in a current cycle.

Claims

1. A battery management system comprising:

a monitoring circuit for monitoring a battery pack that comprises a plurality of cells and for checking an unbalanced condition of said cells in each cycle of a plurality of cycles; and

a charger external to said battery pack and operable for generating a charging current at an output terminal of said charger to said battery pack and for receiving monitoring information from said monitoring circuit, and for adjusting said charging current at said output terminal from a first level in a previous cycle to a second level that is lower than said first level in response to a detection of said unbalanced condition of said cells in a current cycle,

wherein said monitoring circuit is further capable of checking an undesirable condition of said battery pack in each cycle of said plurality of cycles, and wherein said charger is further capable of adjusting said charging current from said first level in said previous cycle to a third level that is lower than said first level in response to a detection of said undesirable condition in a current cycle.

2. The battery management system as claimed in claim 1, wherein said battery pack comprises a balancing circuit for balancing said plurality of cells if said unbalanced condition is detected.

3. The battery management system as claimed in claim 1, further comprising:

a communication channel coupled between said battery pack and said charger for transferring said monitoring information from said monitoring circuit to said charger,

wherein said monitoring circuit is in said battery pack, and wherein said monitoring information indicates a cell voltage for each cell of said plurality of cells.

4. The battery management system as claimed in claim 1, wherein said unbalanced condition occurs if a voltage difference between two cells of said plurality of cells is greater than a predetermined voltage difference.

5. The battery management system as claimed in claim 1, wherein said monitoring circuit is capable of monitoring said battery pack through said output terminal of said charger, and wherein said monitoring information indicates a battery pack voltage of said battery pack.

6. The battery management system as claimed in claim 1, wherein said unbalanced condition occurs if a differential in battery pack voltage with respect to a differential in charging time is greater than a predetermined threshold.

7. The battery management system as claimed in claim 1, wherein said unbalanced condition occurs if a battery pack voltage of said battery pack is greater than a predetermined voltage.

8. The battery management system as claimed in claim 1, wherein said charger adjusts said charging current to said second level after a predetermined time when said unbalanced condition is detected.

9. The battery management system as claimed in claim 1, further comprising:

a communication channel coupled between said battery pack and said charger for transferring monitoring information from said monitoring circuit to said charger,

wherein said monitoring circuit is in said battery pack, and wherein said monitoring information indicates a cell voltage for each cell of said plurality of cells.

10. The battery management system as claimed in claim 1, wherein said battery pack is operable for switching off a charging switch if said undesirable condition is detected.

11. The battery management system as claimed in claim 1, wherein said undesirable condition comprises an over-voltage condition.

12. The battery management system as claimed in claim 1, wherein said monitoring circuit is capable of monitoring said battery pack through said output terminal of said charger, and wherein said monitoring circuit detects said undesirable condition if said charging current is less than a predetermined current value.

13. A method for charging a battery pack having a plurality of cells, comprising:

monitoring a status of said battery pack;

checking an unbalanced condition of said cells in each cycle of a plurality of cycles;

controlling a charger external to said battery pack to adjust a charging current at an output terminal of said charger to said battery pack from a first level in a previous cycle to a second level that is lower than said first level in response to a detection of said unbalanced condition of said cells in a current cycle;

checking an undesirable condition of said battery pack in each cycle of a plurality of cycles; and

adjusting said charging current of said battery pack from said first level in said previous cycle to a third level that is lower than said first level in response to a detection of said undesirable condition in a current cycle.

14. The method of claim 13, further comprising:

balancing said plurality of cells if said unbalanced condition is detected.

15. The method of claim 13, further comprising:

determining that said unbalanced condition occurs if a voltage difference between two cells of said plurality of cells is greater than a predetermined voltage difference.

16. The method of claim 13, further comprising:

monitoring said status of said battery pack through said output terminal of said charger,

wherein said monitoring information indicates a battery pack voltage of said battery pack.

17. The method of claim 13, further comprising:

determining that said unbalanced condition occurs if a differential in battery pack voltage with respect to a differential in charging time is greater than a predetermined threshold.

18. The method of claim 13, further comprising:

determining that said unbalanced condition occurs if a battery pack voltage is greater than a predetermined voltage.

19. The method of claim 13, further comprising:

adjusting said charging current to said second level after a predetermined time when said unbalanced condition is detected.

20. The method of claim 13, further comprising:

transferring said monitoring information from said monitoring circuit to said charger via a communication channel between said battery pack and said charger,

wherein said monitoring information indicates a cell voltage for each cell of said plurality of cells.

21. The method of claim 13, wherein said undesirable condition comprises an over-voltage condition.

22. The method of claim 13, further comprising:

switching off a charging switch if said undesirable condition is detected.

23. The method of claim 13, further comprising:

determining that said undesirable condition occurs if said charging current is less than a predetermined current value.